The Haynes manual should be OK for minor stuff.
If you want the factory service manuals, go to http://helminc.com . You
can order them on-line. They are the most complete. Not cheap, but well
worth investing in.
Usually a manual that covers more than one vehicle model, may be sketchy
about interior and body components. Such as: door panels, headlamps, dash
boards, gages, etc... Meaning, the things that are different about Chevy,
Pontiac, and Olds. Yes it's the same body, but there are some things
different about each of them.